Gravity Conveyance Wiki
'Introduction and Scope' This Wiki contains information about gravity conveyors. These conveyors, as their name implies, use gravity to move materials and products from place to place. Gravity conveyors are widely used in industry because they do not require power for operations, they require very little maintenance, and they are easy to repair when breakdowns occur. In this Wiki you will find information on how gravity conveyors were used throughout history, and examples of common gravity conveyor systems. You will also find the design parameters and restrictions that need to be considered when utilizing gravity conveyors in materials handling, as well as some references to venders that use gravity conveyors. History and Technology Progression Gravity conveyor systems have been an important part of the manufacturing environment since the early 19th Century. However, these systems have been used long before that. It is assumed that the Ancient Egyptians used primitive roller conveyors to move the massive stones that they used to build their pyramids in 2630 BC. The Romans built gravity conveying aqueducts around 312 BC that continued to supply water to the city for over 500 years. They also used a similar conveyance method to transport waste to bodies of water to keep the city clean. Similar techniques are utilized by manufacturers today to move powders, liquids, and molten materials from place to place within their plants. In 1908, the first roller conveyor was patented in Indiana by Hymie Goddard of Logan Company. Within 5 years, the conveyor business began to boom with the rise of assembly lines and mass production. One of the biggest contribution to gravity conveyance was the success of Henry Ford in 1913, who used them to streamline his assembly line and greatly increase the speed of production of automobiles. Following Ford’s lead, many companies began to devise their own gravity roller systems, helping manufacturing to flourish through two World Wars. The American Standards association developed the first standards for conveyor safety in 1947. In 1970, OSHA was created. It had its own standards for conveyor safety, focusing mostly on reducing noise made by the systems. From the 70s on, gravity conveyors were perfected to be safer, smoother, and more reliable. Today gravity roller conveyors can be found in almost any manufacturing plant, as well as in airports, grocery stores, and freight hubs. Examples Gravity Conveyors Gravity conveyors, as stated earlier, use gravity to move objects from one place to another. These conveyors do not use any other force to move the object down the line except for the force that is already on the object when it enters the conveyor, such as the force the worker puts on the object when it is pushed onto the conveyor. There are a few different types of gravity conveyors: Chutes Chutes are the most basic method of gravity conveyance. Resembling a playground slide, these conveyors use nothing but gravity and a low-friction surface to move the object from one place to another. Chutes are most useful for moving bulk goods such as powders and liquids and are often used to connected two separate handling devices. Because of their simplicity, these conveyors are very inexpensive to use and maintain. However, it is difficult to control the positioning of items when they enter these conveyors, making them not recommended when the object needs to be oriented a certain way when it exits the chute. Some examples of chutes can be seen below: 2047.jpg 5-blue-chute-06.jpg Video Example Gravity Rollers Roller conveyors use cylinders on axles to move products down the line. The rollers and axles are have very low friction so that it takes very little gravitational force to make the rollers rotate. These conveyors are ideal for heavy-duty loads and are more suited for flat-bottomed objects. Roller conveyors are more expensive and require more maintenance than chutes but are still less expensive than powered conveyors due to their use of gravity. Also, roller conveyors force the product to keep its initial orientation when it enters the conveyor all the way to where it exits the conveyor. Some examples of roller conveyors can be seen below: Roller-conveyor-37178-2824517.jpg Gravity-Roller-Conveyors.jpg Video Examples Gravity Wheels Wheel conveyors are very similar to roller conveyors except they use individual wheels instead of evenly spaced rollers to move the product. Wheel conveyors keep the object in its initial orientation like roller conveyors. The advantage of wheel conveyors over roller conveyors is that they are more economic than roller conveyors. However, wheel conveyors are more suited for less heavy-duty loads. Also, some types of wheel conveyors can be expanded and contracted for storage and ease of movement. Some examples of wheel conveyors can be seen below: 485304614 496.jpg Skate-wheel-conveyor-gravity-15426-4001803.jpg Video Example Powered Vertical Conveyors These conveyors do not use gravity as their sole method of transporting materials. Conveyors that fall under this category are powered by a source and may even work against gravity to move objects upwards: Bucket Conveyors Bucket conveyors are powered by a motor and chain or belt and are used to transport materials vertically upward. They are mostly used to move bulk objects such as powders and liquids to the top of a gravity or other type of conveyor. The buckets are unloaded with gravity at the top of the conveyor when the bucket is inverted. Some examples of bucket conveyors can be seen below: bucket-conveyors-250x250.png chain-bucket-lift-6191-3063519.jpg Video Example Vibrating Conveyor Vibrating conveyors have various uses. In a spiral, screw-like shape the vibrations can be used to slowly move bulk materials along the conveying path. Using this method, bulk materials can be fed at a slow pace through the spiral separating clumps, reducing the chances of clogs, and allowing hot material to cool. Because of the spiral shape, this conveyor is save space compared to the amount of conveying surface that would be needed in a horizontal layout. When a vibrating conveyor is set in a nearly horizontal format with a screen, it can be used to sift out smaller parts of bulk materials from the larger parts. This is a method allows for manufacturers to remove nonconformities from bulk products for recycling or removal. Examples of vibrating conveyors can be seen below: tex-flex-2.jpg 0.jpg Video Example Design Parameters Types of gravity conveyors: Gravity Wheel Conveyor-''' The gravity wheel conveyor design is very economical and has a low coefficient of friction, which means it requires little inertia to get a product moving. This conveyor has wheels that rotate independently, which allows the tracking of packages. Wheel conveyors are light weight and are can be assembled and disassembled easily. Packages transported on this conveyor should have smooth bottom surfaces to ensure satisfactory transportation. Cartons, totes, and wooden slip sheets with smooth surfaces are easily conveyed by gravity on wheel conveyors. Wheel conveyors should not be used when conveying bags, soft-bottom cartons, or cans with chimes. Items may be pushed manually along the conveyor or the conveyor may be inclined allowing the force of gravity to move the items. 'Gravity Roller-' The gravity roller conveyor design is by far the most popular conveyor design used today. This conveyor offers good support for the bottom surfaces of the items to be transported. This conveyor can be used for items with irregular surfaces, moving smoothly as long as the bottom surface of the item does not conform to the shape of the rollers. Gravity rollers are used extensively in distribution, packaging, and manufacturing applications. On level conveyors, items are placed on the conveyor and manually pushed along to the next station or operation. These roller conveyors can be positioned on a decline, which would allow the items that are placed on the conveyor to move to the desired location due to gravity. 'Vertical Lifts-' Vertical lifts are used to move materials in factories, warehouses, industrial plans, institutions, or anywhere that products or supplies need to be moved from one level to another. They provide fast, efficient, convenient, and safe access to and from balconies, basements, and between levels in multiple story buildings. These lifts can be installed for through-floor, interior or exterior applications. Within vertical lift designs, there are drivable, portable, and pushable options. The height of vertical lifts vary, depending on the manufacturer and the need of the purchaser. 'Spiral Gravity Chutes- '''Spiral chutes provide a safe and economical way to lower products from work platforms, overhead conveyor lines, or multi-level installations of any kind. Almost anything that you can convey on a gravity, power, or belt line can be moved on a chute system. These chutes are built for smooth even flow and have an efficient and effective design. '''Gravity Chute-' A standard waste chute must have a minimum of 24 inches in diameter and must be made with fire resistant material. Galvanized or stainless steel may be used to meet this requirement. Also, the chute must be properly vented in order to release harmful odors. For safety purposes, sprinklers may need to be added to chutes in case of fires. The sprinkler system should be installed on different levels in order to ensure that water can travel to all areas of the chute if need be. '''Vendor References Gravity conveyors and vertical lifts can be used to serve many different purposes in systems. Advantages and disadvantages of these systems are compared in order to determine which type of system that is most practical for the factory’s needs. Advantages: * Uses little energy compared to other processes * Doesn’t involve toxic chemicals * Can separate materials based on feed sizes * Flexible designs based on desired needs * Low cost of installation * Minimal maintenance required Disadvantages: * Limited to the speed of gravity * Adhesives may cause stoppage * Only works for certain materials * Difficulty of controlling the position of the object Denver Mineral Engineers, utilize a gravity separation system in order to recover minerals in their gold mining process. This method involves focusing on the use of gravity concentration. Gravity concentration is a practice that separates minerals based off their differences in specific gravity. The specific gravity weight is identified as the weight of the same volume of material compared to water. For example, the specific gravity weight of gold (Au) is 19.3 meaning it is 19.3 times dense than water. Denver Minineral Engineers note the differences in weight so a separation process can occur. Gravity chutes can be used in almost any facility for their waste management. Many apartment complexes, and high raise buildings may adopt this type of system. For instance, a gravity waste chute can be designed to discard any unwanted excess materials such as garbage. Vertical lift belt conveyors can be utilized in many different instances. These types of conveyors must be used when objects cannot travel in the vertical directions without some type of power. Airports may utilize this vertical type of transportation method in order to carry luggage. FedEx also utilizes vertical lifting belts to get their packages to the correct location throughout their facility. References and Attributions Abilla, Pete. "Conveyor Systems." Shmula. Shmula LLC, 7 Mar. 2011. Web. 1 Mar. 2015. . "Glossary." MHI. MHI, 7 Mar. 2011. Web. 1 Mar. 2015. . "Gravity Concentration." Gekko. Web. 01 Mar. 2015. . "Gravity-conveyor Chute Section." Google Books. Web. 01 Mar. 2015. . "Gravity Conveyors." BIPCO Inc. ''Birmingham Industrial Products Company Inc. Web. 02 Mar. 2015. . "Gold Mining Process Development." ''Denver Mineral Engineers. Web. 26 Feb. 2015. . “Gravity Separation Technology.” Mineral Technologies. Web. 2 Mar. 2015. http://www.mineraltechnologies.com/gravity-separation-technology “Gravity Waste Chutes.” Farmers Insurance Group. ''Web. 2 Mar. 2015. http://www.farmers.com/pdf/gravity_waste_chutes.pdf "Gravity Roller Conveyors." ''Central Conveyors ''Ltd. Central Conveyors Ltd. Web. 3 Mar. 2015.'' . "Gravity Roller Conveyors."'' Titan Industries Inc. Web. 02 Mar. 2015. . "Sprial Gravity Chutes." ''Ciso-Eagle. ''Cisco-Eagle. Web. 02 Mar. 2015. . "Techspex Blog: Conveyor Roller Systems–Since Recorded History." ''Techspex Blog. 14 July 2014. Web. 2 Mar. 2015. . Category:Browse